Vacuum appliances, such as wet/dry vacuums are well known for use in collecting debris or other material. Conventional wet/dry vacuums typically include a tank mounted on wheels or casters, and a lid having a housing with a motor and impeller assembly attached thereto. The motor and impeller assembly create suction within the tank, which draws debris and/or liquid into the tank via an air inlet to which a flexible hose may be attached. A bag and/or filter within the tank typically prevents incoming debris from escaping, while allowing filtered air to pass to the impeller and escape through an exhaust outlet disposed on a portion of the tank or the lid, for example.
As debris or material collects on the bag or filter, however, the performance of the vacuum decreases. More specifically, small particles of dust or debris block the pores in the bag or filter and less air is able to pass through the bag or filter and, therefore, less air is pulled through the inlet and able to escape through the exhaust outlet. Thus, as the bag or filter becomes dirtier, the performance of the vacuum decreases.
Various indicators have been used in the past to measure the airflow characteristics or pressure within the vacuum cleaner as a way to gauge the airflow through the bag or filter and thus the need to change or clean it. Many of those indicators are expensive to manufacture and/or are subject to malfunction. As a result, there is a need for a low-cost, reliable device to determine whether there is a need to change or clean the bag or filter.